Switch contact



v. H SANDERS Jan. 1, 1935.

SWITCH CONTACT Filed March 1, 1930 111 ite Po wdercd S11 mez- Gna INVENTQR Vizrzuon H. Sanders BY ATTORN EY I j Patented Jnn. 1, 1935 UNITED STAT-ES PATENT QF'FICE swrrcn' CONTACT Vernon H. Sanders, St. Marys, Pa., assignor to Stackpole Carbon Company, St. Marys, Pa., a corporation of Pennsylvania Application March 1, 1930, Serial No.:482,875

9 Claimm (01. zoo-'16s) This invention relates to improvementsin conor copper graphite formed integrally with the tact elements for electrical switches and the metal that constitutes the main body of the conlike and particularly to contact elements molded tact element. t a from powdered material. A preferred embodiment of the invention is 5, Contact elements of silver and graphite, or shown in theaccompanying drawing forming a mixtures of silver, silver and nickel, silver and part of this specification, wherein tungsten, silver and copper or copper and nickel Figure 1 is a perspective view of a contact with carbon preferably in the form of graphite, element embodying the invention; have heretofore been proposed for uses where Fig. 2 is a front elevation of a switch assemthe expense of such elements is of secondary imbly with a portion of the casing broken away 10 portance. Contact elements of these materials to show the contact elements; I are generally known and hereinafter referred to Fig. 3 is a plan view of the lower section of as silver-graphite" materials. Contact elea mold employed in forming the contact elements formed in their entirety of these materials ment; are too expensive for general industrial uses. The contact element 1 of the present inven- 15 Copp co e ts a used for general tion, illustrated in Figs. 1 and 2 of the accomindustrial purposes, although the operating "panying drawing, comprises a body portion 2 hara of the ne n act e m s in and an integral face portion 3 of silver graphite. e j y of such s a e much inferior to The body portion 2 of the contact element is the p r n of the Silver aphite contact eleformed of copper or such other metal or metal 20 mentS- o instance, it is common wledge compound as will meet the particular use for that a coating of copper oxide frequently forms which the contact element is intended. Since between h Contact faces 0f D 0 w tch the contact element is shaped from molded jaws and causes objectionable contact losses in powdered materials, in a manner later to be the switch. This interferes with the proper described, it can be of such form and dimension 25 functio f t Switch. d also results in as to best meet the particular requirements for overheating and possible welding together of the which it is intended.

switch jaws and otherwise in unsatisfactory op- The copper body portion of the t t 1 eration. ment is of sufiiciently rugged character and of e Present invention contemplates eontaet proper material to adequately support the rela 30 element havin a body po ion o c pper or i e tively thin layer of facing material 3 so that it relatively in pen iv and ru material. and will not be broken up or loosened from the body a contact Su of S v p e like portion because of mechanical strains or -the terial hat is int a y J d 0 the Contact transmission of electrical currentsf-therebody durin t Operation f orming the conthrough. The body portion also is a good contact ele nt o P d te ials. This ductor of electricity and is in suchintimate con- Provides a Contact element having an of the tact with the facing material as to provide very vantages f m together i the .good electrical and mechanical connection be ruggedness and inexpensivecharacteristics of a tween the two materials even when the f i 40 copper contact element.' A contact element of material is relatively thin. 0 E 'f' i 'g g indpstrlial uses The silver graphite facing material 3 extends 1 3 g igg z z s'z i g g y over the entire contact face and well over onto one object of the present invention is to the tip portion of the contact element, so that electrical arcs formed between two such con 48 ggf g zfi ggi f g ggg gg element tact elements will break from the protected 5 Another object is to provide i inexpensive faces of the elements rather than from exposed contact element, particularly for switch con- Portions the f of the elementstacts, having a relatively thin contact face com- The iii-0mg 'matellal 15 formed of a 50 posed of one of the above mentioned non-weldgraphite 0r metal-carbon compound. p 50 ing materials and made integral with the matei a p e o de ant opo t o s v nic el. rial forming the body of the contact element. tungsten, or mixtures of these metals as the me- Another object is to provide acontact element .tallic ingredient that is used in association with molded from powdered material'which is faced graphite or carbon. A preferred composition 66 with silver, silver graphite, silver nickel graphite for the contact face comprises ninety percent of powdered silver and ten percent of powdered graphite.

Because of the high current-carrying capacity of contact elements made in accordance with this invention, such contact elements may be used for electrical machinery requiring the transmission of heavy currents.

In addition, contact elements embodying the invention may be applied to delicate apparatus in which high conductivity between engaging silver graphite surfaces is desired. In such applications the contact pressure that is used may be relatively small as compared with the required pressure for copper contact elements. Such contact elements are also suitable for use where they are subjected to hot electrical arcs experienced in the transmission of relatively high currents.

Contact elements of the type herein proposed may also be made up in slab form and later separated into individual contact elements.

The body and facing material, of the contact element are simultaneously formed from powdered materials in a suitable mold next to be described, so that the facing material is integrally joined to the body portion throughout its entire area and somewhat intermixed therewith at the juncture of the -materials. This produces an inexpensive 'contact element of improved conductivity and superior operating characteristics.

The use of contact elements embodying the invention is illustrated in a conventional switch structure shown in Fig. 2 of thedrawing wherein the housing 4 of the switch mechanism is broken away to more clearly show the contact elements.

A suitable mold for forming contact elements of the above character is shown in Fig. 3 of the drawing. The mold there shown comprises a bottom section 5 that preferably has a removable mold block 6 mounted therein. The mold block 6 has a suitable molding cavity 7 formed therein. The mold cavity '7 has a removable partition member 17 positioned therein, so that it is substantially parallel with the side wall of the mold cavity that serves to form the contact face of the contact element 1 that is shown therein. This partition member 17 is preferably formed of thin sheet metal and is spaced a sufficient distance from the side wall of the mold cavity to provide the desired thickness of contact facing material.

The bottom section 5 has upstanding pins 12 on which a top mold section may be centered and guide posts 15 provided with holes 14 to receive wedges for locking the mold sections.

In the molding operation, material to form the body of the contact element, such as powdered copper, is introduced into the larger compartment of the mold cavity on one side of a partition 17, as shown in Fig. 3. Silver-graphite also in powdered form and preferably of substantially the same fineness, is introduced into the mold cavity upon the opposite side of the partition 17. The partition 17 is then withdrawn, permitting the powdered material on opposite sides thereof to settle and occupy the space left by the partition, whereby the two powdered materials are brought into intimate contact and are somewhat intermixed along their juncture by removal of the partition 1'7. The top mold section is then placed in position and the mold subjected to relatively high pressure in a hydraulic or other form of press. A pressure of seven tons per square inch has been found satisfactory. The mold sections are then locked together. If a heated mold is not used, the mold is removed from the press and placed in an oven which is held at a suitable baking temperature that is determined by the particular powdered materials used. The mold is subjected to this temperature for a few minutes. For the material here suggested 300 F. has been found satisfactory. The material within the mold is then again subjected to compacting pressure, such as ten tons per square inch,. the mold wedges are driven more firmly into place and the mold assembly is heated to a'materially higher temperature, such as 900 F.,- for a period of about onehalf hour, depending upon the materials used. After the second baking of the contact body under pressure at this elevated temperature, the mold is removed from the oven and, if desired, the mold assembly may again be subjected to hydraulic pressure to further consolidate the material of the contact element. The contact'elementor slab of contact elements is then removed from. the mold in substantially completed form.

In the above-described process of manufacture, the preliminary and final baking operations may be carried on in the same mold or, if desired, two mold units may be used so that the powdered material is compacted in the first mold unit by the application of about seven tons per square inch pressure and heated for about three minutes in this mold at 300F. The element may then be transferred to a second mold, where it is baked for about thirty minutes at 900 F., or until the element is properly baked. The element is then further compacted by a pressure of about ten tons per square inch in the mold in which it. was last baked. The above procedure produces a particularly rugged contact element.

If a slab of material from which contact elements are to be cut is to be made, then powdered copper is spread evenly over the bottom of the mold cavity, a thin layer of silver graphite is spread evenly over the layer of copper, and the materials are compressed and baked by either of the above methods. Such a contact sections for making a plurality of contact elements from the one slab.

It will thus be seen that I have provided a contact element having all the advantages of a silver-graphite element, but which can be manufactured at much less cost.

It will also be noted that the composite contact element is composed of parts integrally united with each other and not subject to separation in service.

It will also be apparent to those skilled in the art that this composite body is capable of many modifications and adaptations in both form and composition to meet different needs. lt is to be understood that the particular apparatusshown and described, and the particular procedure set forth are presented for purposes of explanation and illustration of the invention and that various modifications of said apparatus and procedure can be made without departing from the invention as defined in the appended claims.

What I claim is:

1. An integrally molded contact element having a metallic body and a contact face of different material composed of a mixture of metal and carbon in which the carbon is in the form of finely divided particles uniformly interspersed in the metal.

2. A contact element having a metallic body portion, and a contact face consisting of a thin layer of material integrally united to' the body and composed principally of silver.

3. A contact element having a metallic body portion, and a contact face composed of silver having finely divided particles of carbon uniformly interspersed therein.

4. A contact element having a metallic body portion and a contact face of different composition formed of graphite and metallic powder.

5. An integrally molded contact element comprising a copper body portion and a contact race of silver graphite so disposed as to cover all arcing and contacting faces of the element.

6. An integrally molded contact member having a body portion or copper and a contact face comprising a thin layer of metal or metals mixed with graphite.

7. A molded composite contact element composed of a metal body and a thin layer of a difierent composition forming a contact face integrally united to the body.

8. A composite integrally molded contact element comprisinga body portion formed of powdered metal, and a contact face portion formed of powdered silver and graphite, the materials of the body portion and of the face portion being intermixed along the juncture of the materials.

9. A circuit interrupter contact comprising a composite contact member made of a layer of finely divided particles of copper and a layer of finely divided particles of an anti-flux and silver compressed into a solid composite mass.

VERNON H. SANDERS. 

